1. Field of the Invention
The present invention relates to a medical device for cutting a cornea.
2. Background Information
There have been developed a number of different surgical techniques to correct hyperopic or myopic conditions of a human eye. U.S. Pat. No. 4,840,175 issued to Peyman discloses a procedure wherein a thin layer of corneal tissue is cut and removed from a cornea. A laser beam is then directed onto the exposed corneal tissue in a predetermined pattern. The laser beam ablates corneal tissue and changes the curvature of the eye.
U.S. Pat. No. 5,135,726 issued to Ruiz et al. discloses a device for cutting the cornea to expose an underlying surface for laser ablation. Such a device is commonly referred to as a microkeratome. The Ruiz microkeratome includes a ring that is placed onto a cornea and a blade that is located within an opening of the ring. The device also contains a drive mechanism which moves the blade across the cornea in a first direction while sliding the blade across the eye in a second transverse direction. The result is a flap of the cornea. The cut portion can be pulled back to expose an underlying surface.
The drive mechanism disclosed in the Ruiz patent includes a gear assembly which moves the blade across the eye in the first direction. The Ruiz device also contains an eccentric pin which is rotated to slide the blade across the cornea in the second direction. The gear assembly and the eccentric pin are both driven by a single motor.
Once the device is assembled the relative movement of the blade in the first and second directions and the corresponding shape of the corneal cut is fixed. The radius and shape of the cut cannot be varied without changing the gear assembly of the device. It would be desirable to provide a microkeratome that would readily allow a surgeon to change the shape and/or size of the cut.
It has been found that during a microkeratome procedure an eye lash may enter the gear assembly and prevent further movement of the blade. Such an event may require the surgeon to remove the blade during an intermittent point in the cut and complicate the procedure. It would therefore also be desirable to provide a microkeratome that was less susceptible to jamming than microkeratomes of the prior art.
One embodiment of the present invention is a medical device that can be used to cut a cornea. The device includes a blade that is located within an opening of a ring. The ring can be placed onto a cornea. The device may further have a first drive mechanism that moves the blade in a first direction and a separate second drive mechanism that moves the blade in a second direction.